The blood pressure of living organisms is adjusted by the sympathetic nervous system and the balance between the pressor system and the antihypertensive system. Deeply concerned with the pressor system is the renin-angiotensin system. Renin acts on angiotensinogen to produce angiotensin I. The angiotensin I is further converted to angiotensin II by an angiotensin converting enzyme. The angiotensin II has a strong vasoconstriction action, as well as acts on adrenal cortex to promote secretion of aldosterone, thereby increasing blood pressure. Since angiotension II acts via angiotensin II receptor on cell membranes, an antagonist thereof can, like an inhibitor of angiotensin converting enzyme, be used as a therapeutic agent for hypertension caused by angiotensin II.
While there have hitherto been known peptide angiotensin II antagonists represented by Saralasin, they are not effective by oral administration since they are peptide agents. However, there have recently reported nonpeptide angiotensin II antagonists (e.g. Japanese Patent Unexamined Publication Nos. 71074/1981, 501020/1991, 95181/1991, 236377/1991, 271288/1991), and they have been confirmed to be effective by oral administration.
Accordingly, an object of the present invention is to provide a nonpeptide compound having superior angiotensin II antagonism, which is efficacious by oral administration.